“Effective” in this context means the vaccine invokes neutralizing antibodies and T-cell responses to the preferred targets on SARS Co V 2.
Obviously, they have not done exposure experiments.
If you are not at the head of the line for vaccine, keep an eye on people who get exposed or infected after vaccination to make sure that the immune response called forth by the vaccine is not harmful. It is possible that Pfizer has some infected vaccine recipients, we will not see the full data set for months, if then.
Thank you, President Trump.
I have not heard of T-cell response only neutralizing antibodies after the booster. Do you have a link to that information?